/* @flow */

/**
 * unicode letters used for parsing html tags, component names and property paths.
 * using https://www.w3.org/TR/html53/semantics-scripting.html#potentialcustomelementname
 * skipping \u10000-\uEFFFF due to it freezing up PhantomJS
 */
export const unicodeRegExp =
    /a-zA-Z\u00B7\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u037D\u037F-\u1FFF\u200C-\u200D\u203F-\u2040\u2070-\u218F\u2C00-\u2FEF\u3001-\uD7FF\uF900-\uFDCF\uFDF0-\uFFFD/;

/**
 * Check if a string starts with $ or _
 * 检查字符串是否是 $ 或 _ 开头
 * 0x24 $, 0x5f _
 */
export function isReserved(str: string): boolean {
    const c = (str + '').charCodeAt(0);
    return c === 0x24 || c === 0x5f;
}

/**
 * Define a property.
 */
export function def(obj: Object, key: string, val: any, enumerable?: boolean) {
    Object.defineProperty(obj, key, {
        value: val,
        enumerable: !!enumerable,
        writable: true,
        configurable: true
    });
}

/**
 * Parse simple path.
 */
const bailRE = new RegExp(`[^${unicodeRegExp.source}.$_\\d]`);
export function parsePath(path: string): any {
    if (bailRE.test(path)) {
        return;
    }
    const segments = path.split('.');
    return function (obj) {
        for (let i = 0; i < segments.length; i++) {
            if (!obj) return;
            obj = obj[segments[i]];
        }
        return obj;
    };
}
